Explaining the theoretical biological origin of spirituality has no more impact on our need for, and enjoyment of, religious experiences than explaining that water is "only H2O" strips water of its actual meaning. We know what water is. But it's also fun to jump into and play in, good to drink, beautiful to look at, exciting to sail on, capable of putting one to sleep with the sound of lapping waves, useful for baptizing babies in, responsible for inspiring Turner to paint, and wet - even after one knows that there is no such thing as "wet" or "dry" because wet is merely a set of sensations that we call "wetness" caused by a configuration of molecules that are neither dry nor wet. So here's one answer to the question "What is water?" It might also be a partial answer to [atheist writer Daniel] Dennett's claim that he doesn't know whom to thank: Lucy loves her bath!
Lucy loving her bath and smiling while she kicks and splashes all the water out of the baby tub is also "why" water exists. The pleasure we take in a baby's pleasure might be a hint of what our meaning is too: the pleasure of God enjoying our pleasure at existing in the midst of, as Dennett calls it, "all this wonderful stuff."
-Frank Schaeffer, Patience With God (pg. 66)